JPH11317884A - Horizontal deflection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust a correction amount of horizontal linearity and to reduce an amplitude of a horizontal deflection current. SOLUTION: In this horizontal deflection circuit, a switching element 11 is placed across an S-shape correction capacitor 5 connecting in series with a horizontal deflection coil 4, the switching element 11 is made conductive during the horizontal blanking period to discharge charges in the S-shape correction capacitor 5 and an on-time of the switching element 11 is controlled to correct the linearity of the horizontal period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cathode ray tube (CRT).
The present invention relates to a horizontal deflection circuit suitable for use in a television display device or the like using the same.

[0002]

2. Description of the Related Art In general, a horizontal deflection circuit used in a television receiver using a cathode ray tube (CRT) is as shown in FIG. 7, which is provided between a collector and an emitter of a horizontal output npn transistor 1 constituting a switching element. , A damper diode 2 and a resonance capacitor 3 are connected in parallel, and a series circuit of a horizontal deflection coil 4 and an S-shaped correction capacitor 5 is connected in parallel between the collector and the emitter of the horizontal output transistor 1. The collector is connected to the positive electrode of the DC power supply 7 via the primary winding of the flyback transformer 6, and the emitter of the horizontal output transistor 1 is connected to the negative electrode of the DC power supply 7.

As shown in FIG. 7, in the horizontal deflection circuit, in the horizontal scanning section, the horizontal output transistor 1 or the damper diode 2 is in a conductive state, and the equivalent circuit is as shown in FIG. As is clear from FIG.
In the horizontal scanning section, the horizontal deflection current is supplied to the S-shaped correction capacitor 5.
And the horizontal resonance coil 4 maintains the resonance.

However, at this time, the circuit elements such as the horizontal deflection coil 4, the horizontal output transistor 1, and the damper diode 2 consume power, so that the amplitude of the horizontal deflection current gradually decreases during the horizontal scanning period. The horizontal deflection current amplitude at the end of the horizontal scanning section has a smaller value than the horizontal deflection current amplitude at the start of the horizontal scanning section.

Since the horizontal deflection coil 4 has an internal resistance, the voltage between both ends of the horizontal deflection coil 4 is reduced by the product of the horizontal deflection current and the internal resistance. Therefore, as the horizontal deflection current increases, the amount of change in the current decreases.

Generally, an image display device horizontally scans from the left side to the right side of the screen, and when viewed from an image on the CRT screen, the right side of the image appears to be shrunk, so that it is called "shrink right". .

In order to correct the right contraction, many television receivers, computer displays, and the like use a supersaturated reactor called a horizontal linearity coil (or transformer). The core of the horizontal linearity coil (or transformer) is a magnet, and the magnetic material of the core is saturated in the current range used.

For this reason, this horizontal linearity coil (or transformer) has the property that the inductance varies depending on the direction in which current flows. If this horizontal linearity coil (or transformer) is connected in series with the horizontal deflection coil 4 so as to have the largest inductance at the start of horizontal scanning, the impedance of the horizontal deflection coil 4 is apparently large in the first half of horizontal scanning. In the latter half of horizontal scanning, the horizontal deflection current is reduced by the power consumption of the horizontal deflection circuit.
Since the inductance of the horizontal linearity coil (or transformer) is reduced, the apparent impedance of the horizontal deflection coil 4 is reduced, and the current amplitude can be maintained.

[0009]

In the correction using the horizontal linearity coil (or transformer), the effect is determined by the material of the magnetic material used for the horizontal linearity coil (or transformer) and the strength of the magnet. The relationship between the current and the inductance has a property that changes more or less steeply, and the correction effect tends to have a portion where the linearity changes abruptly in accordance therewith, and there is a disadvantage that it is difficult to obtain an ideal correction effect.

In addition, since the amount of deflection current differs between the upper and lower portions of the screen and the center portion, the correction amount also changes.
As a result, pincushion imbalance on the left and right of the screen occurs.

In the correction using the horizontal linearity coil (or transformer), the amount of correction is changed in the vertical scanning cycle to solve problems such as pincushion imbalance, but the correction characteristics cannot be adjusted.

Therefore, in the correction using the horizontal linearity coil (or transformer), when the center of the horizontal deflection and the center of the screen are not aligned due to the variation of the picture tube and the horizontal deflection coil 4, the ideal position is obtained. Since a typical correction characteristic cannot be obtained, a new horizontal centering circuit is required to adjust the characteristic.

Further, since the horizontal linearity coil (or transformer) is used in series with the horizontal deflection coil 4, the impedance of the horizontal deflection coil 4 must be set to a correspondingly small value, and the amplitude of the horizontal deflection current must be reduced accordingly. There was an inconvenience of becoming large.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to adjust the correction amount of the horizontal linearity and to reduce the amplitude of the horizontal deflection current.

[0015]

The horizontal deflection circuit according to the present invention comprises:
A switching element is provided between both ends of an S-shaped correction capacitor connected in series to the horizontal deflection coil, and the switching element is turned on during a horizontal retrace period to discharge the charge of the S-shaped correction capacitor. By controlling the ON time of the switching element, linearity correction of a horizontal cycle is performed.

According to the present invention, the correction amount of the horizontal linearity can be varied by controlling the ON time of the switching element. Therefore, even if the amplitude of the horizontal deflection current changes, the correction amount of the horizontal linearity can be adjusted appropriately. Can be easily obtained.

Further, according to the present invention, there is no component inserted in series with the horizontal deflection coil for this horizontal linearity correction, and no extra voltage drop occurs, so that the impedance of the horizontal deflection coil is set large. The horizontal deflection current amplitude can be kept small.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a horizontal deflection circuit according to the present invention will be described below with reference to FIGS. In FIG. 1, the portions corresponding to FIG. 7 are denoted by the same reference numerals.

In the example shown in FIG. 1, a damper diode 2 and a resonance capacitor 3 are connected in parallel between the collector and the emitter of a horizontal output npn transistor 1 constituting a switching element, and the collector and the emitter of the horizontal output transistor 1 are connected in parallel. A series circuit of a horizontal deflection coil 4 and an S-shaped correction capacitor 5 is connected, and the collector of the horizontal output transistor 1 is connected to a DC power supply terminal 7a to which a positive DC voltage is supplied via a primary winding of a flyback transformer 6. And the emitter of the horizontal output transistor 1 is grounded.

In this embodiment, the connection point between the deflection coil 4 and the S-shaped correction capacitor 5 is connected to a DC blocking capacitor 10.
And a switching element 11 of a composite element composed of a diode and a transistor. That is, the switching element 11 is connected in parallel with the S-shaped correction capacitor 5.

The connection point between the capacitor 10 and the switching element 11 is connected to the choke coil 1 for blocking high frequency.
2 to the DC power supply terminal 7a.

In this embodiment, the switching element 1
1 is turned on during the retrace period of horizontal scanning as shown in FIG. 2A, and the ON time is made variable (pulse width modulation of the switching pulse).

The horizontal deflection circuit of FIG. 1 performs the same horizontal deflection operation as the conventional example of FIG. In this case, the voltage between both ends of the S-shaped correction capacitor 5 is set to the DC power supply terminal 7a as shown in FIG.
Has a sinusoidal waveform centered on the DC voltage E supplied to the.

The DC component of the voltage at the connection point between the switching element 11 and the capacitor 10 is blocked by the capacitor 10, but the DC component from the DC power supply terminal 7 a is superimposed via the choke coil 12. For,
As shown in FIG. 2C, the sine wave is formed around the DC voltage E supplied to the DC power supply terminal 7a.

Next, the operation of the horizontal linearity correction circuit according to this embodiment will be described. As shown in FIG. 2A, a switching signal for turning off the switching element 11 during a horizontal scanning period and turning on the switching element 11 during a retrace period is supplied to a control terminal 11a of the switching prevention 11 as shown in FIG. 2A.

Since the horizontal deflection current flows using the S-shaped correction capacitor 5 as a power supply during the horizontal scanning period, the change rate of the horizontal deflection current and the voltage across the S-shaped correction capacitor 5 are in a proportional relationship.

Therefore, when the horizontal deflection current is attenuated in the latter half of the horizontal scanning period, the voltage across the S-shaped correction capacitor 5 also decreases in the latter half of this horizontal scanning period (see the dotted line in FIG. 2B).

During the retrace period, the switching element 11
Is turned on, a current flows from the S-shaped correction capacitor 5 through the switching element 11, and the voltage across the S-shaped correction capacitor 5 decreases. As a result, the timing at which the voltage across the S-shaped correction capacitor 5 rises is delayed, so that the voltage across the S-shaped correction capacitor 5 decreases in the first half of the horizontal scanning period, and the S-shaped correction occurs in the second half of the horizontal scanning period. This results in an increase in the voltage across the capacitor 5 (see the solid line in FIG. 2B).

When the ON time of the switching element 11 is lengthened, a current flows from the S-shaped correction capacitor 5 through the switching element 11 correspondingly, so that the timing at which the voltage across the S-shaped correction capacitor 5 rises is further delayed. That is, the correction amount can be increased.

Therefore, by modulating the ON time of the switching element 11 in the vertical scanning cycle, the correction amount of the horizontal linearity can be changed in the vertical scanning cycle, and thereby the left and right pincushion imbalance can be corrected.

In this case, since the ON time of the switching element 11 is during the horizontal flyback period, there is no large change in the correction amount during the horizontal scanning period, and the correction using the conventional horizontal linearity coil is inevitable. A rapid change in volume is unlikely to occur.

Further, according to this embodiment, there is no component inserted in series with the horizontal deflection coil 4 for this horizontal linearity correction, and no extra voltage drop occurs, so that the impedance of the horizontal deflection coil 4 is set large. In addition, the horizontal deflection current can be reduced.

In the case of using a conventional horizontal linearity coil, a horizontal centering circuit was required.
In this example, the correction characteristic can be easily controlled by the ON time of the switching element 11, so that by changing the phase of the video signal and the ON time of the switching element 11,
Since the center position of the screen can be adjusted, the horizontal centering circuit can be omitted.

FIG. 3 shows another example of the embodiment of the present invention. 3 will be described, the same reference numerals are given to portions corresponding to the example of FIG.

In the horizontal deflection circuit shown in FIG. 3, a parallel circuit of a switching element 31, a damper diode 32, and a resonance capacitor 33 having a horizontal output, and a parallel circuit of a switching element 21, a damper diode 22, and a resonance capacitor 23 are connected in series. Then, power is supplied to the connection point via the primary winding of the flyback transformer 6. The other end of the switching element 31 is grounded, the horizontal deflection coil 4 is connected to the other end of the switching element 21, and an S-shaped correction capacitor 5 is connected in series to the horizontal deflection coil 4. The other end is grounded.

In such a horizontal deflection circuit, pulse reading circuits 37 and 27 for reading the voltage between both ends of the switching elements 31 and 21, and a switching element control circuit 50 for calculating ON and OFF of the switching element 21 based on the voltages. It has.

Next, this circuit operation will be described with reference to FIGS.
This will be described with reference to FIG. In FIG. 3, a horizontal drive signal is input to the horizontal output switching element 31, and the horizontal output switching element 31 is turned on. At the same time, the switching element control circuit 50 is also operated, and the switching element 21 is also turned on. In this state, a deflection current flows through the horizontal deflection coil 4. On the other hand, switching element 3
1 turns off before the switching element 21 starts a retrace period (horizontal retrace period). During this retrace period, the switching element 21 is turned on / off by the switching element control circuit 50. A series of these operations will be described using an equivalent circuit by separating a horizontal deflection period.

<Trace section a> Trace section a is a state in which both of the switching elements 31 and 21 are conducting.
The equivalent circuit is as shown in FIG. 5A, which has the same form as the one-stage horizontal deflection circuit conventionally used. At this time, both the deflection current and the flyback transformer current increase at a slope corresponding to the voltage across the S-shaped correction capacitor 5 and the power supply voltage, respectively. FIG. 4D shows the waveform of the deflection current at this time.

<Initial of Retrace Period> To enter the retrace period, the switching element 31 is first turned off by a horizontal drive signal. At this time, since the switching element 21 is still conducting, the equivalent circuit is as shown in FIG. 5B, which is the same as a normal horizontal deflection circuit except that there are only two resonance capacitors. At this time, flyback transformer 6
And the current flowing through the horizontal deflection coil 4 flows into the resonance capacitor 33 to generate a voltage at both ends of the resonance capacitor 33, whereby the current starts an inversion operation. That is, the voltage and current waveforms including the resonance operation become the section b in FIG.

<Off-Period of Switching Element 21 in Retrace Section> In the latter half of the retrace section, after the deflection current reaches 0, even if the switching element 21 is turned off, the equivalent circuit remains in FIG. 5C, the equivalent circuit when the switching element 21 is turned off before the deflection current reaches 0 in the first half of the retrace is as shown in FIG. 5C, and another resonance capacitor is connected in series with the horizontal deflection coil 4. 23 has been connected.

Since the deflection current also flows into the resonance capacitor 23, a voltage is also generated at both ends of the resonance capacitor 23, and a pulse voltage larger than the pulse at both ends of the switching element 31 is applied to both ends of the horizontal deflection coil 4. (See FIG. 4A).

Here, the peak value of the retrace pulse voltage at both ends of the switching element 11 is uniquely determined by the power supply voltage, the ratio of the retrace time and the trace time, and is constant. Therefore, this pulse (see FIG. 4B) is flyback. The voltage can be raised by the transformer 6 to a high voltage used for an electron gun of a CRT.

<Latter Half of Retrace Section> In the retrace section, when all the electric charges flowing into the resonance capacitors 33 and 23 flow out and the voltage at both ends becomes 0, the damper diode automatically conducts and ends (the diode is simple for simplicity). Ideal diode). Here, the resonance capacitor 2
Since the current flowing into the capacitor 3 is always smaller than the current flowing into the resonance capacitor 33, the resonance capacitor 23 loses its charge earlier, and the damper diode 22 conducts earlier than the damper diode 32. For this reason, the pulse generated at both ends of the switching element 21 has a smaller pulse width than the pulse generated at both ends of the switching element 31 (see section c in FIGS. 4B and 4C).

Further, if the OFF timing of the switching element 21 is delayed, the current flowing into the resonance capacitor 23 is further reduced.
The pulses at both ends of 1 have a narrower pulse width and a lower pulse height. That is, by controlling the phase of the off timing of the switching element 21,
The retrace pulse voltage applied to both ends of the horizontal deflection coil 4 can be controlled, and as a result, the amplitude of the deflection current can be varied.

Note that the equivalent circuit of the section d in FIG. 4 is the same as that of the section b, so that the description is omitted.

<Trace Section e> When the damper diode 22 conducts, the circuit returns to the equivalent circuit shown in FIG. 5B and the voltage across the resonance capacitor 33 becomes zero.
The retrace operation is continued in the same manner as in the ordinary deflecting circuit, and returns to the equivalent circuit shown in FIG. In this trace section e, the horizontal deflection coil 4 connects the damper diode 32,
A horizontal deflection current flows in the forward direction 22 (see FIG. 4D).
During this time, the switching elements 31 and 21 are kept in a conductive state to prepare for the next trace section a.

As described above, the horizontal deflection current is equal to the deflection sections a,
By repeating b, c, d, and e, the horizontal deflection coil 4 forms a horizontal deflection magnetic field.

Next, a detailed description will be given of a method for controlling the off timing of the switching element to vary the amplitude of the horizontal deflection current to adjust the pincushion distortion and the horizontal image size.

Maximum amplitude (PP value) of horizontal deflection current Ipp
Is proportional to the integral value of the retrace pulse voltage applied to both ends of the horizontal deflection coil during the retrace period. However, since the retrace pulse voltage is about 1200 to 2200 volts, it is divided into a low voltage that can be processed, this voltage is compared with a reference voltage representing the amplitude of horizontal deflection, and the difference is integrated. The feedback is applied to the drive signal of the switching element so that the integrated value becomes 0,
It is intended to control the horizontal deflection current Ipp with high accuracy. The switching element control circuit 50 shown in FIG. 3 is an example.

In this embodiment, the pulse reading circuit 37,
At 27, the retrace pulse voltage applied to both ends of the switching elements 31 and 21 is detected. Note that this detection voltage is obtained by dividing the retrace pulse voltage by using capacitor division or the like. This detected voltage is input to the switching element control circuit 50, and the subtracted voltage is supplied to a subtracter 5 such as an operational amplifier.
Using 1, the retrace pulse voltage (divided value) of the switching element 21 is subtracted from the retrace pulse voltage (divided value) of the switching element 31. The comparator 52 compares the difference voltage with an amplitude control voltage corresponding to a predetermined horizontal amplitude. Usually, a parabolic voltage for correcting pincushion distortion is added to this amplitude control voltage.

Then, the compared voltage is integrated by the integrator 53 to become a DC voltage, which is input to the phase adjuster 54 as a signal for adjusting the phase (off timing) of the drive signal of the switching element 21. The timing pulse generated by the phase adjuster 54 is applied to the drive waveform generator 55
, A drive signal sufficient to drive the switching element 21 is formed. By such a feedback loop, the switching element 21 outputs a deflection current while controlling the off timing.

The above is the operation in the case where the closed-loop control system at the off timing is in a stable operation state. However, depending on the circuit configuration, different operations may be performed during a transitional period such as a rise at power-on. You need to be careful.

In the control system shown in FIG. 3, the area obtained by subtracting the voltage waveform (division value) of the retrace pulse of the switching element 21 from the voltage waveform (division value) of the retrace pulse of the switching element 31 is the amplitude of the deflection current. Changes linearly with respect to And when the power supply rises,
The feedback loop operates so that a retrace pulse does not occur at both ends of the switching element 21 until the area of the subtraction reaches a certain size. That is, until the retrace pulse at both ends of the switching element 31 reaches a certain peak value, no retrace pulse is generated at both ends of the switching element 21, so that a stable rise is obtained.

The horizontal linearity correction circuit of the example shown in FIG. 3 grounds a connection point between the horizontal deflection coil 4 and the S-shaped correction capacitor 5 via a series circuit of a DC blocking capacitor 10 and a switching element 11. 10
Further, the connection midpoint of the switching element 11 is connected to the DC power supply terminal 7a via the choke coil 12. The operation of the horizontal linearity correction circuit turns off the switching element 11 during the horizontal scanning period and turns on the switching element 11 during the retrace period.

Since the horizontal deflection current flows using the S-shaped correction capacitor 5 as a power source in the scanning section, the change rate of the horizontal deflection current and the voltage across the S-shaped correction capacitor 5 have a proportional relationship. Therefore, when the deflection current is attenuated in the latter half of the scanning section, the voltage across the S-shaped correction capacitor 5 also decreases in the latter half of the scanning section (dotted line in FIG. 2B). Figure 2 during the flyback
When the switching element 11 is turned on by a switching signal as shown in A, a current flows from the S-shaped correction capacitor 5 through the switching element 11, and the voltage between both ends decreases. This delays the timing at which the voltage at both ends of the S-shaped correction capacitor 5 rises, so that the voltage at both ends decreases in the first half of the scanning period and rises in the second half (solid line in FIG. 2B).

When the ON time of the switching element 11 is lengthened, a current flows from the S-shaped correction capacitor 5 through the switching element 11 correspondingly, so that the timing at which the voltage across the S-shaped correction capacitor 5 rises is further delayed, The amount of correction can be increased. Therefore, by modulating the switching ON time in the vertical scanning period, the horizontal linearity correction amount can be changed in the vertical scanning period.

According to the example shown in FIG. 3, a voltage of about 2 kV can be applied to the horizontal deflection coil 4 by using two switching elements 31 and 21, and the horizontal deflection current of double-speed scanning is made equal to that of normal scanning. A horizontal deflection circuit capable of reducing power consumption and significantly reducing costs can be obtained.

It should be noted that the horizontal linearity correction circuit according to the present invention is not limited to the above-described example, and various modifications can be considered. For example, as shown in FIG. 6, the DC blocking capacitor 1 of FIGS.
0 may be connected to the horizontal deflection coil 4 in series.

Further, the present invention is not limited to the above-described example, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0060]

According to the present invention, the correction amount of the horizontal linearity can be varied by controlling the ON time of the switching element, so that the correction amount of the horizontal linearity can be properly adjusted even if the amplitude of the horizontal deflection current changes. Can be easily obtained.

According to the present invention, there is no component inserted in series with the horizontal deflection coil for the correction of the horizontal linearity, and no extra voltage drop occurs. Therefore, the impedance of the horizontal deflection coil is set large. The horizontal deflection current can be reduced, which is advantageous in terms of power consumption or cost.

According to the present invention, the horizontal centering circuit can be omitted, which is advantageous in cost. Further, according to the present invention, a steep change in the correction amount of the horizontal linearity is less likely to occur than in the related art.

According to the second aspect of the present invention, by using two switching elements, a voltage of about 2 kV can be applied to the horizontal deflection coil, and the horizontal deflection current for double-speed horizontal scanning is made similar to ordinary horizontal scanning. Since this horizontal linearity correction circuit is incorporated in a horizontal deflection circuit which can reduce power consumption and significantly reduce costs, there is a greater effect in terms of power consumption, cost, and correction characteristics.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of an embodiment of a horizontal deflection circuit of the present invention.

FIG. 2 is a diagram for describing the present invention.

FIG. 3 is a configuration diagram showing another example of the embodiment of the present invention.

FIG. 4 is a diagram for explaining FIG. 3;

FIG. 5 is an equivalent circuit diagram for explaining FIG. 3;

FIG. 6 is a connection diagram showing another example of a main part of the present invention.

FIG. 7 is a configuration diagram showing an example of a conventional horizontal deflection circuit.

FIG. 8 is an equivalent circuit diagram for explaining FIG. 7;

[Explanation of symbols]

1,11,21,31 switching element, 2,2
2,32mm damper diode, 3,23,33mm
Resonance capacitor, 4 horizontal deflection coil, 5 S-correction capacitor, 6 flyback transformer, 7 DC power supply, 7a DC power terminal, 10 capacitor
12 ‥‥ choke coil, 27, 37 ‥‥ pulse reading circuit, 50 ‥‥ switching element control circuit

Claims (2)

[Claims] A switching element is provided between both ends of an S-shaped correction capacitor connected in series to a horizontal deflection coil, and the switching element is turned on during a horizontal retrace period to discharge a charge of the S-shaped correction capacitor. A horizontal deflection circuit for controlling the on-time of the switching element to correct the linearity of a horizontal cycle. 2. One end of a first parallel circuit in which a first switching element, a first damper diode, and a first resonance capacitor are connected in parallel, and the other end of the first parallel circuit is connected to a second end. Is connected to one end of a second parallel circuit in which a switching element, a second damper diode, and a second resonance capacitor are connected in parallel, and the other end of the first parallel circuit is connected to a primary winding of a flyback transformer. The other end of the second parallel circuit is grounded through a series circuit of a horizontal deflection coil and an S-shaped correction capacitor, and the first switching element is switched by a horizontal drive signal. In a horizontal deflection circuit provided with a switching element control means for controlling an off start time and an off period of the second switching element, both ends of the S-shaped correction capacitor A switching element is provided to turn on the switching element during a horizontal flyback period to discharge the charge of the S-shaped correction capacitor, and to control the on time of the switching element to correct the horizontal cycle linearity. A horizontal deflection circuit.